This invention relates generally to at least partial removal of occlusive material from a body vessel with acoustic phenomena resulting from radiation energy pulses delivered through optical fiber media to the vessel, and, more specifically, to methods and apparatus for generating flow within a body lumen to facilitate disruption of occlusive material and recanalization of the occluded vessel. The term xe2x80x9cclotxe2x80x9d is used herein to refer to a thrombus, embolus or some other total or partial occlusion of a vessel. The term xe2x80x9cemulsifyxe2x80x9d means to break apart or disrupt by photoacoustic or mechanical or other phenomena into particle(s) smaller than the original occlusive material.
Various embodiments for delivering radiation energy to body lumens for ablative and photoacoustic recanalization have been previously disclosed. However, none of these embodiments is capable of generating fluid flow within the vessel that can be used to improve the degree of emulsification of an occlusion.
Therefore, it is an object of the present invention to provide techniques and apparatus that use pulsed radiation energy to generate fluid flow and/or to perform mechanical work within body lumens.
It is another object of the present invention to recanalize body vessels by disrupting total or partial occlusions using the disclosed flow techniques and apparatus.
It is a further object of the present invention to provide improved techniques for removing obstructions or occlusions from vessels or lumens within the human body, particularly clots from cerebral blood vessels, where that clot has caused ischemia or an ischemic stroke, and more particularly for use in the timely removal of such a clot without causing collateral damage to the vessel.
It is an object of the present invention to provide a method (and apparatus) for attracting occlusive material to the photoacoustic source of disruption so as to potentially enhance the amount and/or degree of emulsification.
It is another object of the present invention to improve flexibility of the distal tip to improve the ability of the apparatus to access remote, tortuous vessel pathways.
Some or all of these objects are achievable with the various embodiments disclosed herein.
These and other objects are accomplished by the various aspects of the present invention, wherein, briefly and generally, a device having at least one inlet port, at least one outlet port (which may be distal from or proximal to the external environment), and at least one optical fiber having a distal end positioned relative to the ports such that when pulsed radiation energy is delivered to a body vessel via the optical fiber, fluid is caused to pass through the inlet port and to travel towards the outlet port, preferably past the optical fiber distal end. The repetitive formation and collapse of bubbles in the ambient fluid creates this flow phenomenon, which in turn results from the repetitive absorption of radiation pulses by the fluid. This flow phenomenon can be used to enhance the total or partial mechanical disruption or emulsification of occlusions with photoacoustic phenomena (as described in the ""858 application) by causing ambient fluid and occlusive material to be drawn towards the recanalization apparatus. The invention can also result in localized emulsification of occlusive material or partial or complete removal of that material from the body. The capability of radiation energy to cause mechanical work to be performed is demonstrated by the present invention.
Multiple fibers can be arranged in such a manner that one or more fibers generate the pumping phenomenon and/or one or more fibers contribute to the clot emulsification by generating the acoustic phenomena described in the ""858 application, and/or one or more fibers contribute to mechanical disruption of the clot as disclosed herein, for example. Multiple outlet ports are arranged in various tubing materials in such a way as to maintain a flexible distal tip portion of the apparatus while also maintaining column strength of the distal portion.
The use of very small diameter optical fibers allows the desired pumping to be achieved and acoustic waves to be generated with a relatively low amount of radiation pulse energy, thereby keeping the amount of heat input to the vessel at a low level. Proper thermal management according to the present invention reduces the likelihood of damaging the walls of the blood vessel adjacent the occlusion, which is especially important for the relatively thin walled vessels of the brain in which the present invention has application. Further, it is desirable that radiation pulses not causing the desired fluid flow or not being efficiently converted into the desired acoustic waves be terminated in order to prevent inputting energy that heats the region without doing useful work, as has been described in the related applications.